After reading the forums and looking through the web GUI, I was under the impression one's linode had to be shut down to safely initiate a clone, but that the original could be restarted safely after that but before the clone completed. I assumed the underlying LVM on the host would take a snapshot. I started my clone, and just to be on the safe side (eg to avoid silent corruption or something) I checked on IRC, and tasaro informed me that this was not the case.

This leads me to a few things that are either usability bugs or feature requests:

-If a clone is under way and it's not safe to mount the filesystem rw, it shouldn't be possible to boot the original as long as it's not safe to do so. I won't have data loss now that I know the clone can't be trusted, but a clearer warning and GUI safeguards would be appreciated.
-Alternately, using the underlying LVM to snapshot the disk would be fine.
-There's no way that I can see to cancel a clone in progress, which can take some time to complete.

Progress for clones is something that has been discussed and is soon to be implemented similar to the image transfer progress recently implemented. At the time the disk duplication was implemented we weren't yet using LVM but now that all hosts are using LVM it is something to look at implementing.

I figured it was a work in progress. The perfect time for feedback.

It's quite a useful feature, even with the above. It's still easier than what I would have done otherwise.